The present invention relates to a portable terminal apparatus such as a cellular phone which has display sections for displaying various kinds of information on one surface and its rear surface, and a display device used in the portable terminal apparatus.
Conventionally, some portable terminal apparatuses, which are designed to be able to changeably and selectively take a form with a covered main display section or a form with an uncovered (exposed) main display section, have a sub display section on its rear surface in addition to the main display section.
An example of a portable terminal apparatus having a plurality of display sections is a cellular phone constituted by, e.g., foldably or stretchably connecting two housings. An apparatus of this type can present information such as time or an incoming call notification to the user through the sub display section even when the main display section is kept covered. An apparatus of this type is very preferable for a user in terms of operability and convenience, and various models that are commercially available are very popular.
As shown in FIG. 14, in a display device in a portable terminal apparatus, a main LCD (Liquid Crystal Display) 51 and a backlight 53 that trans-illuminates the main LCD 51, and a sub LCD 52 and a backlight 53′ that trans-illuminates the sub LCD 52 are bonded to both surfaces of a frame 54, respectively, by a bonding means such as a double-faced tape (not shown). Additionally, as for the display device in this portable terminal apparatus, the main LCD 51 and sub LCD 52 are arranged in a housing 61 of the portable terminal apparatus such that they can be seen from the user through a main screen 62 and sub screen 63, respectively.
With this arrangement, the main display section having the main LCD 51 and main screen 62, and the sub display section having the sub LCD 52 and sub screen 63 display various kinds of information for the user by trans-illumination from the corresponding backlights.
In the above-described conventional portable terminal apparatus, however, the backlights 53 and 53′ are arranged in the main display section and sub display section, respectively, to illuminates the display sections. For this reason, two backlights are arranged in the display device.
More specifically, the backlights 53 and 53′ have LEDs (Light Emitting Diodes) 53a and 53a′, light guide plates 53b and 53b′, and reflecting sheets 53c and 53c′, respectively. Since two sets of components are necessary, the thickness and weight of them increase the total thickness and weight, and the cost also increases.
For example, to illuminate both the main display section and the sub display section to cause the user to make use of them, the backlights 53 and 53′ must be simultaneously turned on. For this reason, power is consumed by the two backlights.
Generally, a portable terminal apparatus operates by an internal power supply. For this reason, when the power consumption increases, the continuous operation time shortens.